GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. 329 



Their colour is diverse ; they may be very pale parotid gland ; or very 

 dark liver, spleen ; or uniform, or of different shades : varieties which are 

 most frequently due to the mode of distribution of the vessels, or to the 

 presence of certain anatomical elements. The colour of organs is not always 

 the same in the deeper parts and at the surface, especially when they are 

 enveloped by a thick, opaque membrane ; for instance, the testicle. Lastly, 

 the coloration is less intense after death than during life, and particu- 

 larly if the animal to which the organs belonged has been killed by effusion 

 of blood. 



The consistence of organs depends on their internal formation and the 

 nature of their constituent elements ; there are soft organs, such as the 

 lungs, and resisting organs, as the testicles. As a general rule, the consistence 

 of organs diminishes after putrefaction has set in. 



Cohesion is the resistance that organs offer to the forces which tend to 

 tsar them ; it depends upon the texture of the organs, and the more or less 

 abundance in their interior of fibrous and elastic tissue. Cohesion is very 

 different from consistency ; thus, such an organ as the lung may be easily 

 compressed, but may be very difficult to tear. 



If organs are examined with regard to their structure, it will be observed 

 that all have a thin or thick fibrous casing which throws septa into their 

 interior, and which support their proper tissue ; this tissue varies with the 

 nature of the organs. It will also be found that they are traversed by a 

 more or less considerable number of blood-vessels arteries and veins. These 

 vessels expand into a capillary network, whose meshes have a shape closely 

 allied to that of the elements of the proper tissue. The number and volume 

 of the vessels of an organ give an exact idea of its importance, and of the 

 activity of the physiological phenomena taking place in it. Finally, into 

 the composition of organs enter superficial and deep lymphatic vessels and 

 nerves, which generally follow the arteries. The nerves show in their course 

 small ganglionic enlargements ; their mode of termination is most frequently 

 unknown. 



Glands are organs of a particular construction, whose function it is to 

 eliminate certain fluid or solid products of the economy. 



The very simple (or tubular) glands consist of a straight or convoluted 

 tube, or of a small vesicular cavity opening on a tegumentary membrane, and 

 are lined on their inner face by one or more layers of cells. As examples, 

 there may be cited the tubular glands of the intestines and stomach, the 

 racemose (or lobulated) glands of Br (inner, and the solitary follicles of 

 the intestine. 



But there are also conglomerate glands, organs more complex, though 

 belonging to the same groups as the simple glands. These are glands 

 composed of tubes, like the kidneys and testicles ; racemose glands, such as 

 the salivary glands and pancreas; a network of glands, like the liver; or 

 glands with closed follicles, such as the thyroid. In these the essential 

 anatomical element the polygonal, cylindrical, or spherical gland-cell 

 is situated on the inner face of a tube, as in the kidney, or a demi-vesicle, 

 as is seen in the pancreas, or deposited without any order in the meshes of 

 a plexus of canaliculi, as occurs in the liver. 



The conglomerate glands are provided with a common excretory canal, 

 that commences in their mass by a great number of arborescent ramifications. 



The walls of ^this canal are composed of an elastic, and sometimes con- 

 tractile, conjunctival membrane, covered on its inner face by an epithelium, 

 which may or may not be of the same character as that of the gland. 



